rebase: add --detach option to detach intermediate revisions (issue1950)

When rebasing an intermediate revision, rebase keeps a parent relationship
with the original parent. This option forces the removal of this relationship.
In more depth, it 'fakes' null merges between the target revision and the
ancestors of source, dropping every change from the ancestors.
The result is that every change in source and its descendants will be rebased,
ignoring the changes in its ancestors.

tests/test-rebase-detach

@@ -0,0 +1,68
+#!/bin/sh
+
+echo "[extensions]" >> $HGRCPATH
+echo "graphlog=" >> $HGRCPATH
+echo "rebase=" >> $HGRCPATH
+
+BASE=`pwd`
+
+addcommit () {
+    echo $1 > $1
+    hg add $1
+    hg commit -d "${2} 0" -m $1
+}
+
+commit () {
+    hg commit -d "${2} 0" -m $1
+}
+
+createrepo () {
+    cd $BASE
+    rm -rf a
+    hg init a
+    cd a
+    addcommit "A" 0
+    addcommit "B" 1
+    addcommit "C" 2
+    addcommit "D" 3
+
+    hg update -C 0
+    addcommit "E" 4
+}
+
+createrepo > /dev/null 2>&1
+hg glog  --template '{rev}: {desc}\n'
+echo '% Rebasing D onto E detaching from C'
+hg rebase --detach -s 3 -d 4 2>&1 | sed 's/\(saving bundle to \).*/\1/'
+hg glog  --template '{rev}: {desc}\n'
+echo "Expected A, D, E"
+hg manifest
+
+echo
+createrepo > /dev/null 2>&1
+hg glog  --template '{rev}: {desc}\n'
+echo '% Rebasing C onto E detaching from B'
+hg rebase --detach -s 2 -d 4 2>&1 | sed 's/\(saving bundle to \).*/\1/'
+hg glog  --template '{rev}: {desc}\n'
+echo "Expected A, C, D, E"
+hg manifest
+
+echo
+createrepo > /dev/null 2>&1
+hg glog  --template '{rev}: {desc}\n'
+echo '% Rebasing B onto E using detach (same as not using it)'
+hg rebase --detach -s 1 -d 4 2>&1 | sed 's/\(saving bundle to \).*/\1/'
+hg glog  --template '{rev}: {desc}\n'
+echo "Expected A, B, C, D, E"
+hg manifest
+
+echo
+createrepo > /dev/null 2>&1
+hg glog  --template '{rev}: {desc}\n'
+echo '% Rebasing C onto E detaching from B and collapsing'
+hg rebase --detach --collapse -s 2 -d 4 2>&1 | sed 's/\(saving bundle to \).*/\1/'
+hg glog  --template '{rev}: {desc}\n'
+echo "Expected A, C, D, E"
+hg manifest
+
+exit 0

tests/test-rebase-detach.out

@@ -0,0 +1,134
+@  4: E
+|
+| o  3: D
+| |
+| o  2: C
+| |
+| o  1: B
+|/
+o  0: A
+
+% Rebasing D onto E detaching from C
+saving bundle to 
+adding branch
+adding changesets
+adding manifests
+adding file changes
+added 2 changesets with 2 changes to 2 files (+1 heads)
+rebase completed
+@  4: D
+|
+o  3: E
+|
+| o  2: C
+| |
+| o  1: B
+|/
+o  0: A
+
+Expected A, D, E
+A
+D
+E
+
+@  4: E
+|
+| o  3: D
+| |
+| o  2: C
+| |
+| o  1: B
+|/
+o  0: A
+
+% Rebasing C onto E detaching from B
+saving bundle to 
+adding branch
+adding changesets
+adding manifests
+adding file changes
+added 3 changesets with 3 changes to 3 files (+1 heads)
+rebase completed
+@  4: D
+|
+o  3: C
+|
+o  2: E
+|
+| o  1: B
+|/
+o  0: A
+
+Expected A, C, D, E
+A
+C
+D
+E
+
+@  4: E
+|
+| o  3: D
+| |
+| o  2: C
+| |
+| o  1: B
+|/
+o  0: A
+
+% Rebasing B onto E using detach (same as not using it)
+saving bundle to 
+adding branch
+adding changesets
+adding manifests
+adding file changes
+added 4 changesets with 4 changes to 4 files
+rebase completed
+@  4: D
+|
+o  3: C
+|
+o  2: B
+|
+o  1: E
+|
+o  0: A
+
+Expected A, B, C, D, E
+A
+B
+C
+D
+E
+
+@  4: E
+|
+| o  3: D
+| |
+| o  2: C
+| |
+| o  1: B
+|/
+o  0: A
+
+% Rebasing C onto E detaching from B and collapsing
+saving bundle to 
+adding branch
+adding changesets
+adding manifests
+adding file changes
+added 2 changesets with 3 changes to 3 files (+1 heads)
+rebase completed
+@  3: Collapsed revision
+|  * C
+|  * D
+o  2: E
+|
+| o  1: B
+|/
+o  0: A
+
+Expected A, C, D, E
+A
+C
+D
+E

hgext/rebase.py

@@ -22,6 +22,8 from mercurial.lock import release
 from mercurial.i18n import _
 import os, errno
 
+nullmerge = -2
+
 def rebase(ui, repo, **opts):
     """move changeset (and descendants) to a different branch
 
@@ -53,6 +55,7 def rebase(ui, repo, **opts):
         extrafn = opts.get('extrafn')
         keepf = opts.get('keep', False)
         keepbranchesf = opts.get('keepbranches', False)
+        detachf = opts.get('detach', False)
 
         if contf or abortf:
             if contf and abortf:
@@ -62,6 +65,10 def rebase(ui, repo, **opts):
                 raise error.ParseError(
                     'rebase', _('cannot use collapse with continue or abort'))
 
+            if detachf:
+                raise error.ParseError(
+                    'rebase', _('cannot use detach with continue or abort'))
+
             if srcf or basef or destf:
                 raise error.ParseError('rebase',
                     _('abort and continue do not allow specifying revisions'))
@@ -75,8 +82,16 def rebase(ui, repo, **opts):
             if srcf and basef:
                 raise error.ParseError('rebase', _('cannot specify both a '
                                                    'revision and a base'))
+            if detachf:
+                if not srcf:
+                    raise error.ParseError(
+                      'rebase', _('detach requires a revision to be specified'))
+                if basef:
+                    raise error.ParseError(
+                        'rebase', _('cannot specify a base with detach'))
+
             cmdutil.bail_if_changed(repo)
-            result = buildstate(repo, destf, srcf, basef)
+            result = buildstate(repo, destf, srcf, basef, detachf)
             if not result:
                 # Empty state built, nothing to rebase
                 ui.status(_('nothing to rebase\n'))
@@ -140,10 +155,10 def rebase(ui, repo, **opts):
                                                         state, targetancestors)
             commitmsg = 'Collapsed revision'
             for rebased in state:
-                if rebased not in skipped:
+                if rebased not in skipped and state[rebased] != nullmerge:
                     commitmsg += '\n* %s' % repo[rebased].description()
             commitmsg = ui.edit(commitmsg, repo.ui.username())
-            concludenode(repo, rev, p1, external, commitmsg=commitmsg,
+            newrev = concludenode(repo, rev, p1, external, commitmsg=commitmsg,
                                                     extra=extrafn)
 
         if 'qtip' in repo.tags():
@@ -151,11 +166,13 def rebase(ui, repo, **opts):
 
         if not keepf:
             # Remove no more useful revisions
-            if set(repo.changelog.descendants(min(state))) - set(state):
+            rebased = [rev for rev in state if state[rev] != nullmerge]
+            if rebased:
+                if set(repo.changelog.descendants(min(rebased))) - set(state):
                 ui.warn(_("warning: new changesets detected on source branch, "
                                                         "not stripping\n"))
             else:
-                repair.strip(ui, repo, repo[min(state)].node(), "strip")
+                    repair.strip(ui, repo, repo[min(rebased)].node(), "strip")
 
         clearstatus(repo)
         ui.status(_("rebase completed\n"))
@@ -260,6 +277,9 def defineparents(repo, rev, target, sta
     if P1n in targetancestors:
         p1 = target
     elif P1n in state:
+        if state[P1n] == nullmerge:
+            p1 = target
+        else:
         p1 = state[P1n]
     else: # P1n external
         p1 = target
@@ -379,9 +399,10 def abort(repo, originalwd, target, stat
         clearstatus(repo)
         repo.ui.status(_('rebase aborted\n'))
 
-def buildstate(repo, dest, src, base):
+def buildstate(repo, dest, src, base, detach):
     'Define which revisions are going to be rebased and where'
     targetancestors = set()
+    detachset = set()
 
     if not dest:
         # Destination defaults to the latest revision in the current branch
@@ -400,6 +421,12 def buildstate(repo, dest, src, base):
         if commonbase == repo[dest]:
             raise util.Abort(_('source is descendant of destination'))
         source = repo[src].rev()
+        if detach:
+            # We need to keep track of source's ancestors up to the common base
+            srcancestors = set(repo.changelog.ancestors(source))
+            baseancestors = set(repo.changelog.ancestors(commonbase.rev()))
+            detachset = srcancestors - baseancestors
+            detachset.remove(commonbase.rev())
     else:
         if base:
             cwd = repo[base].rev()
@@ -426,6 +453,7 def buildstate(repo, dest, src, base):
 
     repo.ui.debug('rebase onto %d starting from %d\n' % (dest, source))
     state = dict.fromkeys(repo.changelog.descendants(source), nullrev)
+    state.update(dict.fromkeys(detachset, nullmerge))
     state[source] = nullrev
     return repo['.'].rev(), repo[dest].rev(), state
 
@@ -468,9 +496,11 cmdtable = {
         ('', 'collapse', False, _('collapse the rebased changesets')),
         ('', 'keep', False, _('keep original changesets')),
         ('', 'keepbranches', False, _('keep original branch names')),
+        ('', 'detach', False, _('force detaching of source from its original '
+                                'branch')),
         ('c', 'continue', False, _('continue an interrupted rebase')),
         ('a', 'abort', False, _('abort an interrupted rebase')),] +
          templateopts,
-        _('hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--keep] '
-                            '[--keepbranches] | [-c] | [-a]')),
+        _('hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] '
+                        '[--keep] [--keepbranches] | [-c] | [-a]')),
 }

tests/test-rebase-parameters.out

@@ -2,7 +2,7
 
 % Use continue and abort
 hg rebase: cannot use both abort and continue
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
 
 move changeset (and descendants) to a different branch
 
@@ -21,6 +21,7 options:
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
+    --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
@@ -30,7 +31,7 use "hg -v help rebase" to show global o
 
 % Use continue and collapse
 hg rebase: cannot use collapse with continue or abort
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
 
 move changeset (and descendants) to a different branch
 
@@ -49,6 +50,7 options:
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
+    --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
@@ -58,7 +60,7 use "hg -v help rebase" to show global o
 
 % Use continue/abort and dest/source
 hg rebase: abort and continue do not allow specifying revisions
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
 
 move changeset (and descendants) to a different branch
 
@@ -77,6 +79,7 options:
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
+    --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file
@@ -86,7 +89,7 use "hg -v help rebase" to show global o
 
 % Use source and base
 hg rebase: cannot specify both a revision and a base
-hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--keep] [--keepbranches] | [-c] | [-a]
+hg rebase [-s REV | -b REV] [-d REV] [--collapse] [--detach] [--keep] [--keepbranches] | [-c] | [-a]
 
 move changeset (and descendants) to a different branch
 
@@ -105,6 +108,7 options:
     --collapse      collapse the rebased changesets
     --keep          keep original changesets
     --keepbranches  keep original branch names
+    --detach        force detaching of source from its original branch
  -c --continue      continue an interrupted rebase
  -a --abort         abort an interrupted rebase
     --style         display using template map file